At launch, the RT-N66U was limited to 32k nvram. However, CFE (bootloader) version 1.0.1.3 added 64k nvram support around April 2013, but was not compatible with DD-WRT firmware at that time. For details, see these forum links to historical nvram and 64K implemention discussions: Fractal comments and "RT-N66 CFE Thread"
Jul 06, 2014 Astrill Setup Manual:Getting started with ASUS Merlin Apr 06, 2020 Asus RT-N66U best settings? - Ars Technica OpenForum
None: Remote: Medium: Not required: Complete: Complete: Complete: Global buffer overflow in networkmap in Asuswrt-Merlin firmware for ASUS devices and ASUS firmware for ASUS RT-AC5300, RT_AC1900P, RT-AC68U, RT-AC68P, RT-AC88U, RT-AC66U, RT-AC66U_B1, RT-AC58U, RT-AC56U, RT-AC55U, RT-AC52U, RT-AC51U, RT-N18U, RT-N66U, RT-N56U, RT-AC3200, RT-AC3100, RT_AC1200GU, RT_AC1200G, RT-AC1200, RT-AC53, RT
Asus RT-N66U Firmware Upgrade | AnandTech Forums
Aug 23, 2014
Introducing the ASUS RT-N66U Dual Band N900 Ultra Fast Wireless Router. With 3 x detachable R-SMA type antenna, 50% wider coverage than standard N SPEC, VPN Server function enable and IPv6 support ASUS RT-N66U is a true Business class router yet affordable from regular consumers.Support IPv6.2 years parts and labor warranty. ASUS Merlin Firmware [Guide] - How to flash your ASUS RT-N66U; RT-AC66U; RT-AC56U; Pros and Cons of Asus – Merlin. Not all firmware offers perfection, as, flashing to Asus-Merlin would cost your wireless router to lose AiMesh feature, Asus-Merlin firmware is compatible with AiMesh feature starting from Build 384.13.